The present invention relates to an ink jet dot printer comprising a head mounted on a carriage movable with respect to a support for the printing paper and having a plurality of tubes for ejecting the ink, each tube having a piezoelectric transducer for expelling a drop of ink through a corresponding nozzle in response to a predetermined electric signal.
An ink jet printing head is known in which the ducts containing the ink are obtained in a single block of resin and converge towards a matrix of nozzles aligned vertically in a plate fixed rigidly to the block of resin. The expulsion of the drops of ink is produced by piezoelectric sleeves embedded in the resin coaxially with each duct.
The construction of such a head proves very complex and costly because of the use of moulding cores for forming the ducts, which must be extracted after hardening of the block of resin, with a consequent danger of scoring of the internal surface of the ducts. Moreover, in the event of blockage of one or more nozzles, it is necessary to replace the head, with a consequent loss of time for aligning the new head on the carriage.
The object of the invention is to produce an ink jet printing head of simple construction and high performance which obviates the above-mentioned disadvantages.
A further object of the invention is to provide a driving circuit for the ink jet head, by means of which it is possible to print the characters with a slope which is variable both forward and backward with respect to the vertical.